Linear Density Converter
Convert yarn linear density between tex, denier, dtex and kg/m, plus the cotton and metric count systems, which run backwards from the rest.
Type in any field and the others update instantly. The count systems at the bottom run backwards from the rest, so a higher number there means a finer yarn.
Linear density measures the mass of a fiber or yarn per unit length. It is the standard way to describe thread and yarn thickness in the textile industry.
All conversions use tex as the base unit.
Key units:
- Tex = grams per 1,000 meters (ISO standard)
- Decitex (dtex) = grams per 10,000 meters = tex ÷ 10
- Denier (den) = grams per 9,000 meters = tex × 9
- kg/m = tex ÷ 1,000,000
Conversion formulas:
- 1 tex = 9 denier
- 1 tex = 10 dtex
- 1 denier = 0.1111 tex
- 1 dtex = 0.1 tex
Common fiber reference values (per filament, not per finished yarn):
| Fiber | Denier | Tex |
|---|---|---|
| Microfiber | under 1 | under 0.11 |
| Silk, single strand | 1 | 0.11 |
| Nylon stocking | 10-15 | 1.1-1.7 |
| Cotton thread | 20-40 | 2.2-4.4 |
| Carpet fiber | 15-24 | 1.7-2.7 |
Denier is common in North America for consumer products. Tex and dtex are the ISO standard used in technical specifications.
Denier is the number most people have actually seen, on a package of tights. The higher it is, the thicker and more opaque the fabric: 15 denier is barely-there sheer, 40 to 80 is everyday opaque, and 100-plus is winter warmth. The same logic shows up on fishing line, outdoor gear, and carpet, where a higher denier means a heavier, more durable fiber. It’s a weight rating standing in for thickness.
Why measure mass per length at all, rather than diameter? Because fibers and yarns aren’t smooth round rods. They’re fuzzy, twisted, and irregular, so a caliper reading would be meaningless, while weighing a known length is repeatable and honest.
The count systems run backwards, and that is the trap. Cotton, wool and linen are sold by count, which is an indirect system: it says how many fixed-length hanks make up one pound. More hanks to the pound means a finer thread, so a higher count means a thinner yarn - the exact opposite of denier and tex. A 30s cotton is finer than a 10s. A 150-denier polyester is coarser than a 70-denier. Put a count system and a direct system side by side without noticing and you will reach for precisely the wrong yarn.
| System | Direction | Conversion to tex |
|---|---|---|
| Ne, cotton count | Higher = finer | tex = 590.5 ÷ Ne |
| Nm, metric count | Higher = finer | tex = 1,000 ÷ Nm |
| Nw, worsted count | Higher = finer | tex = 885.8 ÷ Nw |
| Tex, dtex, denier | Higher = coarser | direct |
Those constants are not arbitrary. Cotton count is built on an 840-yard hank and the pound, so 453.59 g ÷ (840 × 0.9144 m ÷ 1,000) works out to 590.54. The worsted hank is 560 yards, giving 885.81. Metric count is the tidy one, a thousand metres to the gram.
A last practical note: a plied yarn multiplies. Two ends of 30s cotton twisted together give a 30/2, which behaves like a 15s in thickness while being stronger and rounder than a singles of the same weight. The converter above handles a single strand; for a plied yarn, divide the count by the number of plies before converting.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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